Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: March 17, 2003
Publication Date: March 17, 2003
Citation: Kerr, B.J. 2003. Physiological and biological limitations for nutrient utilization in farm animals. Journal of Animal Science. 81 Suppl.2): 84. Technical Abstract: Optimizing nutrient utilization by farm animals is vital in maintaining economical animal production in light of environmental concerns associated with agriculture, but is often limited due to numerous physiological and biological factors. It was not long ago that the gastrointestinal tract was hardly considered as an organ of metabolic concern. Its importance, however is clearly evident as Thr, an indispensable amino acid, been shown to be highly metabolized by gastrointestinal tissue. The metabolic fate of Thr is further complicated by the fact that crystalline Thr, which is a readily available feed ingredient, is more rapidly absorbed than protein-bound Thr. Another factor that impacts nutrient utilization is the relationship between diet and gastrointestinal physiology and microbial ecology. It is well known that changing dietary forage has a tremendous impact on rumen microbial ecology. The understanding of this relationship in monogastrics is lacking and complicated by sizeable microbial population that inhabit their lower gastrointestinal tract. Past research in monogastrics dealt mainly with the impact of `fiber' addition on performance with little data describing physiological or microbiological changes. In addition, characterization of the fiber type was lacking such that the changes in dietary fiber consumed could not be calculated. With the current emphasis on supplementing feed ingredients targeted for selective hind gut microbial fermentation, more information is needed on the metabolic and physiological changes in the animal due to fiber supplementation. An additional area of nutrient utilization interest is the low retention of various minerals commonly supplemented in livestock feed, either due to their inability to be adequate digestibility or their controlled metabolic regulation.